Degree Name

Master of Arts (MA)

Semester of Degree Completion

1975

Thesis Director

W. Boyd Spencer

Abstract

The influence of methylphenidate hydrochloride injections on six male Charles River rats displaying schedule induced polydipsia was examined in this study. Bar pressing, licking, and water consumption were measured during a total of 63 daily one hour trials conducted with a variable interval 60-second schedule of bar pressing for pellets with water constantly available. The polydipsic response was acquired by subjects during the first 28 trials. Subjects were then divided into experimental and control groups. The experimental subjects recieved a 1 mg/kg injection of methylphenidate prior to regular trials 29-49 and extinction trials 50-63. Control subjects were injected with a volume of physiological saline during regular and extinction trials. It was hypothesized that methylphenidate injections would affect the bar pressing, licking, and water consumption rates of experimental subjects during the last two phases. An analysis of variance was used to compare the experimental and control groups’ performances for each variable. The analyses included data for the last 14 trials of each of the three phases: acquisition, regular, and extinction sessions, or trials 15-28, 36-49, and 50-63.

Results indicated that there were no significant differences between experimental and control subjects’ rates on any of the variables measured. The only significant main effects were those of the three consecutive phases of the experiment. Possible explanations for the results obtained from the experiment and indications for future research are included in a detailed discussion.

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